Concentraciones de alcaloides, glucósidos cianogénicos, polifenoles y saponinas en plantas medicinales seleccionadas en Ecuador y su relación con la toxicidad aguda contra Artemia salina / Concentrations of alkaloids, cyanogenic glycosides, polyphenols and saponins in selected medicinal plants from Ecuador and their relationship with acute toxicity against Artemia salina

ResumenEntre los principales compuestos químicos sintetizados por las plantas, pero considerados no esenciales para su metabolismo básico, están los alcaloides, los polifenoles, los glucósidos cianogénicos y las saponinas que tienen diversas funciones en las plantas y reconocidas propiedades medicinales y farmacológicas. En esta investigación se determinaron las concentraciones de los mencionados metabolitos secundarios en los extractos de las hojas de las plantas medicinales Taraxacum officinale, Parthenium hysterophorus, Artemisia absinthium, Cnidoscolus aconitifolius y Piper carpunya y se relacionaron con la toxicidad aguda contra Artemia salina. En cada bioensayo con A. salina se usaron los extractos alcohólicos de las hojas de las plantas seleccionadas a diferentes concentraciones, calculándose la proporción de organismos muertos y los CL50. Las concentraciones de alcaloides, fenoles totales, taninos, glucósidos cianogénicos y saponinas fueron determinadas mediante métodos espectrofotométricos. Este es el primer reporte de cuantificación de metabolitos secundarios en las plantas analizadas provenientes de Ecuador. T. officinale presentó las mayores concentraciones de fenoles (22.30 ± 0.23 mg/g) y taninos (11.70 ± 0.10 mg/g), C aconitifolius de glucósidos cianogénicos (5.02 ± 0.37 µg/g) y P. hysterophorus de saponinas (6.12 ± 0.02 mg/g). Las plantas evaluadas presentaron actividades hemolíticas dependiendo de las concentraciones de saponinas. Los valores de taninos determinados estuvieron entre 0.20 ± 0.01 y 11.70 ± 0.10 mg/g, por lo que no son adversos para su consumo. Aunque los valores de glucósidos cianogénicos son permisibles, es necesario monitorear la presencia de estos compuestos químicos en las plantas para minimizar problemas de salud. Los CL50 obtenidos oscilaron entre los valores 3.37 µg/mL, extremadamente letal o tóxica, para P. carpunya y 274.34 µg/mL, altamente tóxica, para T. officinale. De los análisis de correlaciones realizados a los resultados, se observó que los alcaloides favorecen de manera significativa (p<0.001) a la toxicidad aguda contra A. salina, mientras que a mayor contenido de polifenoles dicha toxicidad disminuye significativamente (p<0.001) el nivel de toxicidad de las plantas. Del análisis de componentes principales, se demuestra que las saponinas están en sinergia con los polifenoles para disminuir la toxicidad, pero tienen un efecto antagónico con los alcaloides y los glucósidos cianogénicos, lo cual evidencia que estos metabolitos secundarios presentan variabilidades en los mecanismos de acción contra A. salina, como compuestos citotóxicos. Estos resultados demuestran que las saponinas y los polifenoles pueden ser letales para A. salina a bajas concentraciones, evidenciando que este bioensayo permite evaluar extractos vegetales que contengan bajas concentraciones de compuestos con altas polaridades. La correspondencia significativamente positiva entre citoxicidad y concentración de los alcaloides, confirmada con el bioensayo de Artemia salina, puede ser útil para hallar fuentes promisorias de compuestos antitumorales y para evaluar los límites tolerables que no afecten otras células benignas. El contenido de metabolitos secundarios hallados en las plantas analizadas les atribuye un gran valor farmacológico.

Abstract:Alkaloids, polyphenols, cyanogenic glycosides and saponins are among the main chemical compounds synthesized by plants but not considered essential for their basic metabolism. These compounds have different functions in plants, and have been recognized with medicinal and pharmacological properties. In this research, concentrations of the mentioned secondary metabolites were determined in the medicinal plants Artemisia absinthium, Cnidoscolus aconitifolius, Parthenium hysterophorus, Piper carpunya and Taraxacum officinale, from Ecuador, and related with cytotoxic effects against Artemia salina. Alcoholic and aqueous extracts from leaves of these selected plants were prepared at different concentrations. To assess cytotoxicity of these extracts, different bioassays with A. salina were undertaken, and the mortality rates and LC50 were obtained. Besides, concentrations of alkaloids, cyanogenic glycosides, phenols, tannins and saponins were determined by spectrophotometric methods; this constituted the first report of quantification of secondary metabolites in the selected plants from Ecuador. T. officinale had the highest concentration of total phenols (22.30 ± 0.23 mg/g) and tannins (11.70 ± 0.10 mg/g), C. aconitifolius of cyanogenic glycosides (5.02 ± 0.37 µg/g) and P. hysterophorus of saponins (6.12 ± 0.02 mg/g). Tannins values obtained were not adverse to their consumption. Alcoholic and aqueous extracts of selected plants had hemolytic activity depending on the concentration of saponins. Although the values of cyanogenic glycosides were permissible, it was necessary to monitor the presence of this metabolite in plants to minimize health problems. LC50 values ranged from extremely toxic (3.37 µg/mL) to highly toxic (274.34 μg/mL), in P. carpunya and T. officinale, respectively. From correlation analysis, it was observed that increase values of alkaloids concentrations had highly significant (p<0.001) acute toxicity against A. salina, while at a higher polyphenol concentration the level of plants cytotoxicity decreased significantly (p<0.001). The results of principal component analysis showed that saponins apparently were in synergy with polyphenols to decrease cytotoxicity, but antagonize with alkaloids and cyanogenic glycosides, indicating that these secondary metabolites present variability in the mechanisms of action against A. salina, as cytotoxic compounds. These results also demonstrate that polyphenols and saponins can be lethal at low concentrations, demonstrating the potential of brine shrimp bioassay as a model to evaluate plant extracts containing low concentrations of chemical compounds with high polarities. The significant positive correlation between cytotoxicity and concentration of alkaloids confirmed by the bioassay of brine shrimp can be useful to identify promising sources of antitumor compounds, and to evaluate tolerable limits not affecting other benign cells. Contents of secondary metabolites found in the selected plants confer them great pharmacologic values. Rev. Biol. Trop. 64 (3): 1171-1184. Epub 2016 September 01.

Trypanocidal, trichomonacidal and cytotoxic components of cultivatedArtemisia absinthium Linnaeus (Asteraceae) essential oil

Artemisia absinthium is an aromatic and medicinal plant of ethnopharmacological interest and it has been widely studied. The use ofA. absinthiumbased on the collection of wild populations can result in variable compositions of the extracts and essential oils (EOs). The aim of this paper is the identification of the active components of the vapour pressure (VP) EO from a selected and cultivated A. absinthiumSpanish population (T2-11) against two parasitic protozoa with different metabolic pathways: Trypanosoma cruzi andTrichomonas vaginalis. VP showed activity on both parasites at the highest concentrations. The chromatographic fractionation of the VP T2-11 resulted in nine fractions (VLC1-9). The chemical composition of the fractions and the antiparasitic effects of fractions and their main compounds suggest that the activity of the VP is related with the presence oftrans-caryophyllene and dihydrochamazulene (main components of fractions VLC1 and VLC2 respectively). Additionally, the cytotoxicity of VP and fractions has been tested on several tumour and no tumour human cell lines. Fractions VLC1 and VLC2 were not cytotoxic against the nontumoural cell line HS5, suggesting selective antiparasitic activity for these two fractions. The VP and fractions inhibited the growth of human tumour cell lines in a dose-dependent manner.

In vitro anti-microbial activity of the Cuban medicinal plants Simarouba glauca DC, Melaleuca leucadendron L and Artemisia absinthium L

In the present study, an extensive in vitro antimicrobial profiling was performed for three medicinal plants grown in Cuba, namely Simarouba glauca, Melaleuca leucadendron and Artemisia absinthium. Ethanol extracts were tested for their antiprotozoal potential against Trypanosoma b. brucei, Trypanosoma cruzi, Leishmania infantum and Plasmodium falciparum. Antifungal activities were evaluated against Microsporum canis and Candida albicans whereas Escherichia coli and Staphylococcus aureus were used as test organisms for antibacterial activity. Cytotoxicity was assessed against human MRC-5 cells. Only M. leucadendron extract showed selective activity against microorganisms tested. Although S. glauca exhibited strong activity against all protozoa, it must be considered non-specific. The value of integrated evaluation of extracts with particular reference to selectivity is discussed.